bluetooth.btcommon.BluetoothError: [Errno 2] No such file or directory

I'm trying to connect to a bluetooth device through a Python script using pybluez on a Khadas board (kind of like a Raspberry Pi, aarch64).

I have manually updated PyBluez to 5.65 as it contains a fix I need. Both bluetoothctl --version and bluetoothd --version return 5.65.

Upon launching my script, I get

> python main.py
...
  File "/home/khadas/env/lib/python3.8/site-packages/bluetooth/bluez.py", line 271, in advertise_service
    _bt.sdp_advertise_service (sock._sock, name, service_id, \
_bluetooth.error: (2, 'No such file or directory')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/khadas/copilot/copilot/process/process.py", line 126, in run
    self._pre_run()
  File "/home/khadas/copilot/copilot/task/bluetooth_connector_task.py", line 55, in _pre_run
    bluetooth.advertise_service(
  File "/home/khadas/env/lib/python3.8/site-packages/bluetooth/bluez.py", line 275, in advertise_service
    raise BluetoothError (*e.args)
bluetooth.btcommon.BluetoothError: [Errno 2] No such file or directory

Following this, I have edited /etc/systemd/system/dbus-org.bluez.service and /lib/systemd/system/bluetooth.service to have

ExecStart=/usr/libexec/bluetooth/bluetoothd -C

I then restarted the daemon with

sudo systemctl daemon-reload & sudo systemctl restart bluetooth & sudo sdptool add SP

but my error persists.

Has any of you encountered this before?

Thank you for your time :)

Note: This thread indicates that, following sudo sdptool add SP, a file at /var/run/sdp should have been created; it is not.

Note: The bluetooth service is running, but there are errors, i.e.

(env) khadas@khadas > systemctl status bluetooth.service            
● bluetooth.service - Bluetooth service
     Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2022-08-11 13:23:09 UTC; 13min ago
       Docs: man:bluetoothd(8)
   Main PID: 14256 (bluetoothd)
     Status: "Running"
      Tasks: 1 (limit: 2932)
     Memory: 676.0K
     CGroup: /system.slice/bluetooth.service
             └─14256 /usr/libexec/bluetooth/bluetoothd -C

Aug 11 13:23:09 khadas systemd[1]: Starting Bluetooth service...
Aug 11 13:23:09 khadas bluetoothd[14256]: Bluetooth daemon 5.65
Aug 11 13:23:09 khadas systemd[1]: Started Bluetooth service.
Aug 11 13:23:09 khadas bluetoothd[14256]: Starting SDP server
Aug 11 13:23:09 khadas bluetoothd[14256]: src/sdpd-server.c:init_server() binding UNIX socket: Read-only file system
Aug 11 13:23:09 khadas bluetoothd[14256]: src/sdpd-server.c:start_sdp_server() Server initialization failed
Aug 11 13:23:09 khadas bluetoothd[14256]: Bluetooth management interface 1.14 initialized
Aug 11 13:23:09 khadas bluetoothd[14256]: src/adapter.c:reset_adv_monitors_complete() Failed to reset Adv Monitors: Unknown Command (0x01)

Solution

If you upgrade you also have to update the system service configuration as the new config won't work in this scenario. If you run sudo service bluetooth status you will see that the new config won't start the SDP server correctly:

● bluetooth.service - Bluetooth service
     Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2022-08-23 11:42:36 UTC; 10min ago
       Docs: man:bluetoothd(8)
   Main PID: 3773 (bluetoothd)
     Status: "Running"
      Tasks: 1 (limit: 2934)
     Memory: 2.1M
     CGroup: /system.slice/bluetooth.service
             └─3773 /usr/libexec/bluetooth/bluetoothd -C

Aug 23 11:42:36 biped12 systemd[1]: Starting Bluetooth service...
Aug 23 11:42:36 biped12 systemd[3773]: ConfigurationDirectory 'bluetooth' already exists but the mode is different. (File system: 755 ConfigurationDirectoryMode: 555)
Aug 23 11:42:36 biped12 bluetoothd[3773]: Bluetooth daemon 5.65
Aug 23 11:42:36 biped12 systemd[1]: Started Bluetooth service.
Aug 23 11:42:36 biped12 bluetoothd[3773]: Starting SDP server
Aug 23 11:42:36 biped12 bluetoothd[3773]: src/sdpd-server.c:init_server() binding UNIX socket: Read-only file system
Aug 23 11:42:36 biped12 bluetoothd[3773]: src/sdpd-server.c:start_sdp_server() Server initialization failed
Aug 23 11:42:36 biped12 bluetoothd[3773]: Bluetooth management interface 1.14 initialized
Aug 23 11:42:36 biped12 bluetoothd[3773]: src/adapter.c:reset_adv_monitors_complete() Failed to reset Adv Monitors: Unknown Command (0x01)

To fix this you have to change your config to:

[Unit]
Description=Bluetooth service
Documentation=man:bluetoothd(8)
ConditionPathIsDirectory=/sys/class/bluetooth

[Service]
Type=dbus
BusName=org.bluez
ExecStart=/usr/lib/bluetooth/bluetoothd -C
NotifyAccess=main
#WatchdogSec=10
Restart=on-failure
CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE
LimitNPROC=1
ProtectHome=true
ProtectSystem=full

[Install]
WantedBy=bluetooth.target
Alias=dbus-org.bluez.service